A280591 Fibbinary numbers n such that sigma(n) is also a Fibbinary number.

1, 10, 17, 20, 21, 41, 65, 66, 73, 132, 133, 137, 138, 148, 165, 170, 257, 258, 265, 276, 322, 337, 338, 517, 521, 522, 529, 545, 546, 553, 577, 581, 585, 593, 641, 642, 644, 645, 658, 673, 676, 682, 1032, 1033, 1044, 1097, 1153, 1169, 1172, 1193, 1289, 1297, 1316, 1321, 1361, 1364, 1365

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

Fibbinary number 21 is a term because sigma(21) = 32 is also a Fibbinary number.

Maple

fibbinary:= n -> Bits:-And(n, 2*n)=0:
select(t -> fibbinary(t) and fibbinary(numtheory:-sigma(t)), [seq(i, i=1..2000)]); # Robert Israel, Apr 02 2018

Mathematica

FibbinaryQ[n_] := BitAnd[n, 2 n] == 0; Select[Range[2000] - 1,
FibbinaryQ[#] && FibbinaryQ[DivisorSigma[1, #]] &] (* Ray Chandler, Jan 08 2017 *)

Crossrefs

Cf. A000203, A003714.

Sequence in context: A079630 A175389 A350779 * A308691 A332226 A338590

Adjacent sequences: A280588 A280589 A280590 * A280592 A280593 A280594

Keyword

nonn

Author

Altug Alkan, Jan 06 2017

Extensions

Terms confirmed by Ray Chandler, Jan 08 2017

Status

approved